1. Field of the Invention
The present invention relates to an actuator used in, for example, an electric toothbrush and electric sonic wave toothbrush.
2. Description of the Related Art
Conventionally, for electric toothbrushes including electric sonic wave toothbrushes, bass brushing toothbrushes that place the brush obliquely (at about forty five degrees) on the boundary part between teeth and gum and vibrate the brush left and right in linear back-and-forth motion, and rolling brushing toothbrushes that move in back-and-forth (backward and forward) rotating motion in a range of a predetermined angle around the shaft and rotating the brush from the gum toward teeth, are known.
For the drive of these toothbrushes, structures are commonly employed for making linear back-and-forth motion or back-and-forth rotating motion for rotation of a rotating DC motor, which makes typical rotation around the shaft, through a motion direction converting mechanism. Further, other than these structures, structures for moving a toothbrush in linear back-and-forth motion by a linear drive actuator or structures for moving a toothbrush in back-and-forth rotating motion by resonating a resonance vibrating mechanism, which constitutes a separate entity from the drive source, by the vibration of the actuator, are known.
As disclosed in Japanese Patent Application Laid-Open No. 2002-078310, the structures for moving a toothbrush in linear back-and-forth motion by a linear drive actuator realize bass brushing by directly producing back-and-forth vibration in the axial direction of an output shaft directly connected with the toothbrush part. According to this structure, there is little power loss due to the motion converting mechanism and furthermore high-speed vibration can be performed.
Further, as disclosed in Japanese Patent No. 3243529, a structure with an actuator and a resonance vibrating mechanism which constitutes a separate entity from the drive source, realizes rolling brushing by exciting the resonance vibrating mechanism with a lever arm by a driving means with electric magnets and permanent magnets and by making the lever arm directly connected coaxially with the toothbrush part move in bobble-head motion.
By the way, there is a demand for an electric toothbrush that realizes rolling brushing, and there is also a demand for miniaturization of the drive part of the toothbrush because making slimmer a handle part in which the drive part and driving the rolling brushing toothbrush is demanded.
However, to realize rolling brushing using a motor that makes typical rotation around the shaft, a motion direction converting mechanism for converting the rotation of the motor into back-and-forth rotating motion, is required in addition to the motor. Further, to realize rolling brushing using a linear drive actuator as shown in Japanese Patent Application Laid-Open No. 2002-078310, a torque generating mechanism (i.e. drive source) is required in addition to the linear drive actuator.
Further, the structure disclosed in Japanese Patent No. 3243529 requires a drive source and a resonance vibrating mechanism apart from the drive source.
In this way, to use a motor or linear drive actuator for the drive source of an electric toothbrush, conventional structures need to secure spaces for locating the drive source and, in addition, the motion direction converting mechanism, torque generating mechanism or resonance vibrating mechanism, apart from the drive source and therefore there is a problem that miniaturization of a toothbrush is difficult.
Further, if a drive transmitting mechanism such as a motion direction converting mechanism which constitutes a separate entity from an actuator such as a motor is provided in the drive part of the toothbrush, there are concerns that, in the drive transmitting mechanism, noise is generated and efficiency deteriorates due to occurrence of loss in transmitted power, and therefore countermeasures for these need to be taken into account.